So I just read about Anorgasmia and I do think that condition might turn her off to sex if you are taking forever to climax. It can be painful and pretty annoying, I would think. I don't know about red flags because it seems to me that she is trying to get back to her old self. I am assuming there was a time in the marriage when she ENJOYED sex with you.
Hopefully you do get to the bottom this sooner rather than later. Hopefully the couples therapy will help!